Display panel and display device

ABSTRACT

A display panel includes a first substrate section formed on the front side of the display panel, a second substrate section which is opposed to the first substrate section, a plurality of pixel sections formed in a matrix form between the first and second substrate sections, and a plurality of sensor sections, each of the sensor sections having two electrodes, one electrode disposed with a electrode-to-electrode gap from the other between the first and second substrate sections, the electrode-to-electrode gap being removed as a result of the deformation of the first substrate section under pressure so that the one electrode is brought into contact with the other electrode, the sensor sections being provided between the first and second substrate sections with one of a plurality of electrode-to-electrode gap lengths respectively.

CROSS REFERENCES TO RELATED APPLICATIONS

The present application is a continuation of application Ser. No.12/571,634, filed Oct. 1, 2009, which claims priority to JapanesePriority Patent Application JP 2008-256073 filed in the Japan PatentOffice on Oct. 1, 2008, the entire content of each of which is herebyincorporated by reference.

BACKGROUND

The present application relates to a display panel such as liquidcrystal display panel and a display device having the same.

Various types of displays have been proposed which have sensorcapability and permit so-called touch-panel entries.

For example, Japanese Patent Laid-Open No. 2005-275644 proposes a methodof detecting light reflected from a target in proximity using an opticalsensor formed integrally with the panel.

Further, Japanese Patent Laid-Open No. 2001-75074 (hereinafter referredto as Patent Document 2) describes a method of detecting the pressedposition of the panel as a result of direct contact between electrodesformed inside the panel when the panel is pressed.

Still further, Japanese Patent Laid-Open No. 2007-52369 (hereinafterreferred to as Patent Document 3) proposes a method of forming gapsbetween electrodes based on height differences between different colorsof the color filter.

SUMMARY

However, the existing display panels having sensor capability aredesigned to detect the position of the panel pressed by a finger ortouch pen. A display panel designed to detect the pressing pressure inmultiple levels has not yet to be proposed.

For example, in the direct contact type as in Patent Document 2 adaptedto achieve position detection as a result of direct contact between theelectrodes formed inside the panel when the panel is pressed, thepressing pressure can only be detected using a given threshold. Thismakes it impossible to permit entry of levels of gradation of thepressing pressure.

In the case of forming gaps between electrodes based on heightdifferences between different colors of the color filter as in PatentDocument 3, on the other hand, the height differences in the colorfilter are determined by optical specification such as chromaticity,contrast, transmittance and composition of the color filter material.This makes it impossible to achieve intended height differences.

Further, columns are provided to be shared by the color of the colorfilters with the largest cell thickness. As a result, only as many leveldifferences as the number of colors other than the above color can beformed. This leads to only two levels of the pressing pressureresolution.

In light of the foregoing, it is desirable to provide a display panelwhich permits entry of multiple levels of gradation thanks to a new ideaapplied to the distance between electrodes, i.e., a display panel whichcan detect the pressing pressure in multiple levels. It is stilldesirable to provide a display device capable of determining theintensity of the pressure applied.

A display panel according to an embodiment includes a first substratesection formed on the front side of the display panel. The display panelfurther includes a second substrate section which is opposed to thefirst substrate section. The display panel still further includes aplurality of pixel sections formed in a matrix form between the firstand second substrate sections. The display panel still further includesa plurality of sensor sections. Each of the sensor sections has twoelectrodes, one electrode disposed with a electrode to electrode gapfrom the other between the first and second substrate sections. Theelectrode-to-electrode gap is removed as a result of the deformation ofthe first substrate section under pressure, bringing the one electrodeinto contact with the other electrode. The sensor sections are providedbetween the first and second substrate sections with one of a pluralityof electrode-to-electrode gap lengths respectively.

Further, the pixel sections are liquid crystal pixel sections.

Still further, the sensor sections are each formed for one of the liquidcrystal pixel sections. A pixel electrode and common electrode adaptedto drive the liquid crystal pixel section are used as the one and otherelectrodes.

The one electrode of the sensor section is formed on the firstsubstrate, and the other electrode thereof is formed on the secondsubstrate.

The plurality of sensor sections having different electrode-to-electrodegap lengths are arranged with predetermined regularity between the firstand second substrates.

Further, the plurality of sensor sections form projecting portions ofdifferent heights on the second substrate. The other electrodes arearranged on the projecting portions, thus forming a plurality ofelectrode-to-electrode gap lengths.

Still further, the plurality of sensor sections form projecting portionsof different heights on the first substrate. The one electrodes arearranged on the projecting portions, thus forming a plurality ofelectrode-to-electrode gap lengths.

Still further, the plurality of sensor sections form depressed portionsof different depths on the second substrate. The other electrodes arearranged on the depressed portions, thus forming a plurality ofelectrode-to-electrode gap lengths.

Still further, the plurality of sensor sections form depressed portionsof different depths on the first substrate. The one electrodes arearranged on the depressed portions, thus forming a plurality ofelectrode-to-electrode gap lengths.

Still further, the plurality of different electrode-to-electrode gaplengths are each set based on the relationship between a pressureapplied to the first substrate section and deformation of the firstsubstrate section.

A display device according to an embodiment includes, in addition to theconstituent components of the display panel, a display drive section andsensor read section. The display drive section drives the plurality ofpixel sections to display an image. The sensor read section determinesthe position of the first substrate section to which a pressure isapplied and the amount of pressure applied thereto by detecting eachelectrode contact condition at a plurality of sensor sections.

That is, in an embodiment, each of the sensor sections is set to one ofthe electrode-to-electrode gap lengths. As a result, the sensor sectionshaving a plurality of electrode-to-electrode gap lengths are arrangedbetween the first and second substrates. For example, a sensor sectionis formed for each pixel.

In this case, when a given pressing pressure is applied to a planarposition of the front side of the first substrate section, the severalsensor sections provided near the planar position have their electrodesin different contact conditions according to the electrode-to-electrodegap length. That is, the electrodes of the sensor section with a shortelectrode-to-electrode gap length come into contact with each other evenwhen a small pressing pressure is applied. On the other hand, theelectrodes of the sensor section with a long electrode-to-electrode gaplength do not come into contact with each other until a large pressingpressure is applied.

Therefore, if the sensor sections having a large number ofelectrode-to-electrode gap lengths are arranged, the different sensorsections respond to the pressing pressure (that is, the electrodes ofthe different sensor sections come into contact with each other).Therefore, not only the pressed position but also the level of gradationof the pressing pressure can be detected by detecting the sensor sectionwhich has responded.

An embodiment is effective in that it permits ready entry of levels ofgradation adapted to distinguish between different pressing pressures,unlike existing contact input which can only distinguish between twodifferent states or presence or absence of contact.

Such entry of levels of gradation contributes to increased variety inthe use of touch panel entry and enhanced functionality, includingmaking it possible to provide, for example, an application program whichreads the change in writing pressure and draws brush-drawn-lookingcharacters and images, despite the fact that they are pen-drawn.

Additional features and advantages are described herein, and will beapparent from the following Detailed Description and the figures.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is an explanatory diagram of a video recording deviceincorporating a liquid crystal display device according to anembodiment;

FIG. 2 is an explanatory diagram of the configuration of the liquidcrystal display device according to the embodiment;

FIG. 3 is a waveform diagram describing the operation timings of theliquid crystal display device according to the embodiment;

FIG. 4 is an explanatory diagram of a basic sensor structure accordingto the embodiment;

FIG. 5 is an explanatory diagram of the sensor according to theembodiment when the sensor is pressed;

FIG. 6 is an explanatory diagram of an example of sensor structure withdifferent electrode-to-electrode gap lengths according to theembodiment;

FIG. 7 is an explanatory diagram of another example of sensor structurewith different electrode-to-electrode gap lengths according to theembodiment;

FIG. 8 is an explanatory diagram of still another example of sensorstructure with different electrode-to-electrode gap lengths according tothe embodiment;

FIG. 9 is an explanatory diagram of still another example of sensorstructure with different electrode-to-electrode gap lengths according tothe embodiment;

FIG. 10 is an explanatory diagram of still another example of sensorstructure with different electrode-to-electrode gap lengths according tothe embodiment;

FIG. 11 is an explanatory diagram of still another example of sensorstructure with different electrode-to-electrode gap lengths according tothe embodiment;

FIG. 12 is an explanatory diagram of still another example of sensorstructure with different electrode-to-electrode gap lengths according tothe embodiment;

FIGS. 13A and 13B are explanatory diagrams of examples of settingelectrode-to-electrode gap lengths according to the embodiment;

FIGS. 14A to 14H are explanatory diagrams of an example of arrangementof the sensors according to the embodiment;

FIGS. 15A and 15B are explanatory diagrams of the sensors in a contactcondition according to the embodiment;

FIGS. 16A and 16B are explanatory diagrams of the sensors whoseelectrodes are in contact according to the embodiment; and

FIGS. 17A to 17E are explanatory diagrams of arrangement of the sensorsaccording to the embodiment.

DETAILED DESCRIPTION

A description will be given below of a liquid crystal display panel andliquid crystal display device according to an embodiment of the presentapplication in the following order:

1. Liquid Crystal Panel Structure

2. Sensor Structure

3. Examples of Sensor Structures with Different Electrode-to-ElectrodeGap Lengths

4. Examples of Setting Electrode-to-Electrode Gap Lengths

5. Examples of Arrangement of the Sensors

6. Effects of the Embodiment and Modification Example

1. Liquid Crystal Panel Structure

FIG. 1 illustrates an example of a video recording device (camcorder)100 incorporating the liquid crystal display device (liquid crystaldisplay panel) according to the present embodiment.

The video recording device 100 has a liquid crystal display panel 1. Theliquid crystal display panel 1 displays a monitor image during movingimage recording and a reproduced image during moving image reproduction.The liquid crystal display panel 1 also displays, for example, anoperation menu, icons and thumbnail images. The same panel 1 permitstouch panel operation, accepting operation input made by the user as heor she touches an operation menu item or icon with a finger.

FIG. 2 illustrates a configuration example of a liquid crystal displaydevice having the liquid crystal display panel 1. FIG. 3 illustrates atiming diagram illustrating the operation of the liquid crystal displaydevice.

The liquid crystal display device includes a pixel array. The pixelarray includes a read circuit 2, write circuit 3, drive circuit 4 andpixel circuits 5 arranged therein.

The drive circuit 4 supplies a drive pulse to gate lines (gateelectrodes) GL in sequence every horizontal period. The gate lines GLare disposed one for each of the horizontal lines of the pixel array.

The write circuit 3 outputs a signal level to signal lines LS disposedas vertical lines of the pixel array in synchronism with the driving ofeach of the horizontal lines by the drive circuit 4. The signal level isbased on display data supplied from a display video signal processingcircuit which is not shown. When the signal level is output, a writeswitch Sw is switched ON, connecting the write circuit 3 to each of thesignal lines LS.

The read circuit 2 reads ON/OFF information of a sensor S formed in eachof the pixel circuits 5 in synchronism with the driving of each of thehorizontal lines by the drive circuit 4. When the information of thesensor S is read, a read switch Sr is switched ON, connecting the readcircuit 2 to each of the signal lines LS. The output of the sensor S isconverted to digital data by the read circuit 2. At the same time, thepressed horizontal position (display panel position) and the amount ofpressing pressure are determined based on the detection results of theON/OFF information for one screen.

The pixel circuits 5 each include a liquid crystal cell LC. The liquidcrystal cell LC includes liquid crystal sealed between electrodes (pixelelectrode and common electrode (COM electrode)) opposed to each other.

Further, the pixel circuits 5 each include a pixel transistor Tr. Thepixel transistor Tr has its gate node connected to the gate line GL, itssource node connected to the signal line LS and its drain node connectedto the pixel electrode of the liquid crystal cell LC.

Still further, the pixel circuits 5 each include the sensor S. The pixeland COM electrodes come into electrical contact with each other when anexternal pressure such as pressing pressure by a finger is exerted onthe sensor S. The operation of the liquid crystal display device will bedescribed below with reference to FIG. 3.

FIG. 3 illustrates a gate electrode pulse (Gate) supplied to the givengate line GL by the drive circuit 4, a sensor read signal (Read) adaptedto control the read switch Sr ON and OFF, and write signals (WriteB(blue), WriteG (green) and WriteR (red)) adapted to control the write SwON and OFF. FIG. 3 also illustrates the potentials of the COM electrodeand signal line LS. The sensor read signal (Read) and write signals(WriteB, WriteG and WriteR) are generated respectively by unshowncontrol circuit sections at predetermined timings during a horizontalperiod so as to switch ON the read switch Sr and write switch Sw.

As the basic drive timing, the COM electrode is inverted in polarityfirst. In FIG. 3, a case is shown in which the COM electrode changesfrom L (low) to H (high) level.

Next, all the write signals (WriteB, WriteG and WriteR) change to Hlevel, switching ON all the write switches Sw. At this time, all thesignal lines LS are precharged to the level opposite in phase to that ofthe COM electrode.

Then, the write signals (WriteB, WriteG and WriteR) change to L level,switching OFF all the write switches Sw.

Next, the drive circuit 4 pulls the gate electrode pulse (Gate) up to Hlevel, turning ON the pixel transistors Tr of the horizontal pixelcircuits 5 which are connected to the gate line GL. This connects thepixel electrodes and signal lines LS together.

Next, the sensor read signal (Read) is pulled up to H level, switchingON all the read switches. At this time, the information of the sensors Sof the pixel circuits 5 along a given horizontal line whose pixeltransistors Tr are currently ON by the gate electrode pulse (Gate) isfed to the read circuit 2.

For example, in the case of the sensor S of the pixel circuit 5 in thearea which has not received any input (pressure) from outside the panel,the COM and pixel electrodes are electrically separated from each other(the sensor is OFF). As a result, the input from this sensor S to theread circuit 2, i.e., the potential of the signal line LS, remainsunchanged from the precharged level.

In the case of the sensor S of the pixel circuit 5 in the area which hasreceived an input (pressure) from outside the panel, on the other hand,the COM and pixel electrodes are electrically connected together (thesensor is ON). As a result, the input from this sensor S to the readcircuit 2, i.e., the level of the signal line LS, increases from theprecharged level to the level of the COM electrode.

The read circuit 2 detects this change in signal line level as a resultof the COM and pixel electrodes being brought into or remaining out ofcontact with each other by converting the change into “1” or “0” digitalsignal during a read period (period during which the sensor read signal(Read) is at H level).

The read circuit 2 reads the sensor information from the pixel circuits5 line by line every horizontal period as described above. This allowsfor the information of the sensors S of all the pixel circuits 5 to beread in one frame period.

Then, the read circuit 2 determines the touched position of the screenand amount of touching pressure (level of gradation of the pressureapplied) based on the read information. The pressing pressure can bedetermined because the sensors S are formed with differentelectrode-to-electrode gap lengths as described later.

When the read period of the sensor S information ends, the sensor readsignal (Read) is pulled down to L level, followed by the writing of thesignal level to the pixel circuits 5.

That is, the write signals (WriteB, WriteG and WriteR) change to H levelin sequence. Each time the write switches Sw are switched ON, the writecircuit 3 writes video signal levels respectively to the blue, green andred pixels.

2. Sensor Structure

A description will be given below of the structure of the sensor Sformed in the pixel circuit 5 in the liquid crystal display device whichis configured and operates as described above.

Here, the basic structure thereof will be described with reference toFIGS. 4 and 5.

FIG. 4 schematically illustrates the cross-sectional structure of apixel of the liquid crystal display panel 1.

A color-filter-side glass substrate 10 serves as a substrate on thefront side of the panel. A TFT (thin film transistor)-side glasssubstrate 19 is disposed to be opposed to the color-filter-side glasssubstrate 10. A liquid crystal pixel structure is formed between the twoglass substrates 11 and 19.

In the present example, as illustrated in FIG. 4, a color filter 11 madeof an organic film and an overcoating material 12 are formed on thecolor-filter-side glass substrate 10, and an opposed contact electrode13 serving as one of electrodes making up the sensor S is formed on theovercoating material 12. The COM electrode shown in FIG. 2 is used asthe opposed contact electrode 13. That is, as is clear from the pixelcircuits 5 shown in FIG. 2, the sensors S share the COM electrode as asensor switch electrode.

On the other hand, a pixel electrode 16 adapted to apply an electricfield to the liquid crystal is formed on the TFT-side glass substrate 19via an insulating film 18 and planarizing film 17.

The pixel electrode 16 is the drain node electrode of the pixeltransistor Tr shown in FIG. 2. The pixel electrode 16 is disposed to beopposed to the opposed contact electrode 13 (COM electrode). Liquidcrystal 15 is sealed between the two electrodes, thus forming the liquidcrystal cell LC.

Here, the pixel electrode 16 and opposed contact electrode 13 (COMelectrode) are opposed to each other so as to be separated by apredetermined distance by a spacer 14 adapted to form a liquid crystalgap.

In this condition, a hollow sensor column (hereinafter referred to asthe sensor column) 20 is formed on the planarizing film 17. The pixelelectrode 16 is continuous on the sensor column 20.

In the pixel electrode 16, the top portion of the sensor column 20 andthe opposed contact electrode 13 (COM electrode) which is opposed to thetop portion form the switch structure of the sensor S.

FIG. 5 illustrates an object such as a finger or stylus touching thesurface of the color-filter-side glass substrate 10. As the pressingpressure deforms part of the color-filter-side glass substrate 10, thepixel electrode 16 formed on the top portion of the sensor column 20comes into contact with the opposed contact electrode 13. In the pixelnot pressed with a finger or other object, on the other hand, the pixelelectrode 16 and opposed contact electrode 13 remain separated from eachother as illustrated in FIG. 4.

When the pixel electrode 16 and opposed contact electrode 13 come intocontact with each other as a result of the pressing as illustrated inFIG. 5, the potential of the signal line LS connected to the pixelcircuit 5 in question changes from the precharge level to the level ofthe COM electrode. In the condition shown in FIG. 4, on the other hand,the potential of the signal line LS connected to the pixel circuit 5remains at the precharge level.

During the read period (period during which the sensor read signal(Read) is at H level) described earlier with reference to FIG. 3, theread circuit 2 determines whether the sensor S of the pixel circuit 5 inquestion is ON or OFF by determining the potential of the signal lineLS.

3. Examples of Sensor Structures with Different Electrode-to-ElectrodeGap Lengths

If the sensor S configured as described above is provided in each of thepixel circuits 5, the read circuit 2 can detect which position of thescreen has been pressed by determining whether each of the sensors S isON or OFF during a frame period. That is, it is only necessary todetermine the pixel position whose sensor S is ON.

However, the present embodiment determines not only the touched positionbut also the amount of touching pressure in multiple levels. That is,the present embodiment determines the level of gradation of pressingpressure.

Therefore, the sensors S of the pixel circuits 5 are each arrangedbetween the color-filter-side glass substrate 10 and TFT-side glasssubstrate 19 with their electrodes set to one of a plurality of gaplengths (distances between the pixel electrode 16 and opposed contactelectrode 13).

A description will be given below of various examples of the structurewith reference to FIGS. 6 to 12.

FIG. 6 illustrates an example in which the sensors S have differentelectrode-to-electrode gap lengths in the basic configuration shown inFIG. 4.

It should be noted that the spacers 14 are not formed between every pairof pixels. Instead, in reality, the spacer 14 is provided everypredetermined pixel block (n by m pixels). In FIGS. 6 to 12 describedbelow, examples are shown in which three pixels are providedhorizontally or vertically between a pair of the spacers 14 for reasonsof illustration. In reality, however, the spacers 14 are likely disposedin a further discrete manner in the plane direction.

Further, FIGS. 6 to 12 will be described assuming, for reasons ofsimplicity in description and illustration, that each pixel is set toone of three different electrode-to-electrode gap lengths.

It should be noted that, in FIGS. 6 to 12, the color filter 11 andovercoating material 12 are not shown on the color-filter-side glasssubstrate 10. Further, the insulating film 18 and planarizing film 17are not shown on the TFT-side glass substrate 19.

For example, in the example shown in FIG. 6, the sensor columns 20 ofthe pixels differ in height from one another. That is, a relatively highsensor column 20-1 is formed for the pixel having a pixel electrode16-1. A sensor S1 thereof has a short electrode-to-electrode gap lengthZ1 between a pixel electrode 16-1 and the opposed contact electrode 13.

Further, a slightly low sensor column 20-2 is formed for the pixelhaving a pixel electrode 16-2. A sensor S2 thereof has anelectrode-to-electrode gap length Z2 between a pixel electrode 16-2 andthe opposed contact electrode 13. The electrode-to-electrode gap lengthZ2 is longer than the electrode-to-electrode gap length Z1.

Still further, an even lower sensor column 20-3 is formed for the pixelhaving a pixel electrode 16-3. A sensor S3 thereof has anelectrode-to-electrode gap length Z3 between a pixel electrode 16-3 andthe opposed contact electrode 13. The electrode-to-electrode gap lengthZ3 is longer than the electrode-to-electrode gap length Z2.

That is, in the case of the structure shown in FIG. 6, the sensorcolumns 20-1, 20-2 and 20-3 with different heights are formed one foreach of the pixels. This forms the sensors S1, S2 and S3 of the pixelswith different electrode-to-electrode gap lengths.

As described above, the difference in electrode-to-electrode gap lengthbetween the different sensors S allows for determination of the pressingpressure.

When the sensor is pressed from the side of the color-filter-side glasssubstrate 10, the same substrate 10 bends as illustrated in FIG. 5. Theextent to which the same substrate 10 bends varies depending on thepressing pressure. As a result, which of the sensors S1, S2 and S3 willbe turned ON by the pressing pressure varies depending on the pressingpressure.

For example, when a small pressing pressure is applied, only the sensorS1 turns ON. A larger pressing pressure turns ON the sensors S1 and S2.An even larger pressing pressure turns ON the sensors S1, S2 and S3.

Therefore, if the read circuit 2 knows in advance which structure, i.e.,that of the sensor S1, S2 or S3, each of the sensor S has, the samecircuit 2 can determine the approximate pressing pressure applied bydetermining which pixels are ON.

Normally, when the surface of the liquid crystal display panel 1 ispressed, for example, with a finger, there are many pixels in the areacorresponding to the pressed position. Therefore, if theelectrode-to-electrode gap length is the same for all the pixels as inthe case of existing display devices, the sensors S of the many pixelsin the pressed position are detected to be ON. As a result, the pressedposition of the screen can be detected, but the amount of pressingpressure cannot be determined.

However, if each of the many pixels in the area corresponding to thepressed position has one of the three sensors S1, S2 and S3 havingdifferent electrode-to-electrode gap lengths, the pressed position ofthe panel can be detected at least when the sensor of the pixel havingthe sensor S1 is detected to be ON. In addition, if the sensors of onlythe pixels having the sensors S1 are ON in the area corresponding to thepressed position, it is possible to determine that a relatively smallpressing pressure has been applied. Further, if the sensors of thepixels having the sensors S1 and S2 are ON, it is possible to determinethat a slightly larger pressing pressure has been applied. Stillfurther, if the sensors of the pixels having the sensors S1, S2 and S3are ON in the area corresponding to the pressed position, it is possibleto determine that an even larger pressing pressure has been applied.

As described above, if the sensors S1, S2 and S3 respectively having thedifferent electrode-to-electrode gap lengths Z1, Z2 and Z3 aredistributed one to each of the pixels, it is possible to determine thepressing pressure.

Here, the pressing pressure can be determined in three levels ofgradation for reasons of simplicity in description. Naturally, however,if the sensors S1 to Sn respectively having the n differentelectrode-to-electrode gap lengths Z1 to Zn are distributed among thepixels, it is possible to determine the pressing pressure in n levels ofgradation.

FIGS. 7 to 12 illustrate examples of structures to provide differentelectrode-to-electrode gap lengths.

In FIG. 7, the sensor columns 20-1, 20-2 and 20-3 respectively for thesensors S1, S2 and S3 are the same in height as each other. In thiscase, depressed portions are formed on the color-filter-side glasssubstrate 10. The portions of the opposed contact electrode 13 opposedto the pixel electrodes 16-2 and 16-3 are formed into depressed shapesof different depths. This forms the different electrode-to-electrode gaplengths Z1, Z2 and Z3.

In the structure shown in FIG. 8, the pixel electrodes 16-1, 16-2 and16-3 are disposed two-dimensionally on the TFT-side glass substrate 19.

The sensor columns 21-1, 21-2 and 21-3 with different heights are formedon the color-filter-side glass substrate 10. The opposed contactelectrode 13 is continuous on the sensor columns 21-1, 21-2 and 21-3.This forms the sensors S1, S2 and S3 with the differentelectrode-to-electrode gap lengths Z1, Z2 and Z3.

In the structure shown in FIG. 9, the sensor columns 21-1, 21-2 and 21-3with the same height are formed on the color-filter-side glass substrate10. The opposed contact electrode 13 is continuous on the sensor columns21-1, 21-2 and 21-3. On the other hand, depressed portions of differentdepths are formed on the TFT-side glass substrate 19. The pixelelectrode 16-1 is formed on a flat portion. The pixel electrode 16-2 isformed within and along a shallow depressed portion. The pixel electrode16-3 is formed within and along a deep depressed portion. This forms thesensors S1, S2 and S3 with the different electrode-to-electrode gaplengths Z1, Z2 and Z3.

In the case of this structure, the formation of the depressed portionstructure can be incorporated in the photo process for the TFT arrayside. This makes the present structure advantageous in that it can formthe sensors S1, S2 and S3 with the different electrode-to-electrode gaplengths Z1, Z2 and Z3 without adding any process steps.

In the structure shown in FIG. 10, the sensor columns 20-1, 20-2 and20-3 with different heights are formed on the TFT-side glass substrate19. On the other hand, a structure 22 in a uniform projecting shape isformed over an area of the color-filter-side glass substrate 10 opposedto the pixel electrodes 16-1, 16-2 and 16-3 respectively on the sensorcolumns 20-1, 20-2 and 20-3. The opposed contact electrode 13 iscontinuous on the structure 22. This forms the sensors S1, S2 and S3with the different electrode-to-electrode gap lengths Z1, Z2 and Z3.

This structure is advantageous in that the electrodes are automaticallyexposed because PI is rejected on the structure 22.

In the structure shown in FIG. 11, the sensor columns 20-1, 20-2 and20-3 with the same height as the spacers 14 are provided on the TFT-sideglass substrate 19. Depressed portions are formed on thecolor-filter-side glass substrate 10. The portions of the opposedcontact electrode 13 opposed to the pixel electrodes 16-1, 16-2 and 16-3are formed into depressed shapes of different depths. This forms thedifferent electrode-to-electrode gap lengths Z1, Z2 and Z3.

This structure is advantageous in that the spacers 14 and sensor columns20-1, 20-2 and 20-3 can be formed together in a single process step.

In the structure shown in FIG. 12, the sensor columns 20-1, 20-2 and20-3 with the same height as the spacers 14 are provided on thecolor-filter-side glass substrate 10. Depressed portions are formed onthe TFT-side glass substrate 19. The pixel electrodes 16-1, 16-2 and16-3 are formed within and along depressed portions of different depths.This forms the different electrode-to-electrode gap lengths Z1, Z2 andZ3.

This structure is advantageous in that the spacers 14 and sensor columns20-1, 20-2 and 20-3 can be formed together in a single process step.

Although examples of structures of the sensors S1, S2 and S3 with thedifferent electrode-to-electrode gap lengths Z1, Z2 and Z3 have beendescribed above, it is a matter of course that there are other possibleexamples of structures.

Further, it is needless to say that the structural examples shown inFIGS. 6 to 12 are applicable when four or more differentelectrode-to-electrode gap lengths are formed.

4. Examples of Setting Electrode-to-Electrode Gap Lengths

The present embodiment allows for determination of not only the touchedposition but also the level of gradation of the pressing pressure bydistributing the sensors S with different electrode-to-electrode gaplengths one in each of the pixels as described in the above examples.

It should be noted that when the sensor S is provided in a pixel usingthe pixel electrode 16 and opposed contact electrode 13 (COM electrode)in the pixel circuit, the plurality of sensors S can be formed in asingle pixel (single pixel circuit 5). However, it is not necessary toprovide the plurality of sensors S with different electrode-to-electrodegap lengths in a single pixel. That is, even if the plurality of sensorsS with different electrode-to-electrode gap lengths are provided in asingle pixel, the potential detected by the read circuit 2 is always thepotential of the electrodes which come into contact with each otherfirst. Therefore, even if the electrodes of the next sensor S come intocontact with each other, the potential remains unchanged. As a result,it is not possible to determine whether the electrodes of the sensor Sfor the next level have come into contact with each other.

Therefore, the sensors S with different electrode-to-electrode gaplengths are distributed, one in each of the pixels.

Incidentally, in order to determine the pressing pressure properly, theplurality of electrode-to-electrode gap lengths must be set based on therelationship between the pressing pressure applied to thecolor-filter-side glass substrate 10 and the deformation of the samesubstrate 10 by the pressing pressure. A description will be given belowin this respect.

The relationship between the pressing pressure applied to the glasssubstrate (color-filter-side glass substrate) 10 and the change in theelectrode-to-electrode distance (change in the electrode-to-electrodegap length Z) is determined uniquely by the glass thickness, spacerdensity (density of provision of the spacers 14) and physical propertiesof the material.

Further, when the glass thickness, spacer density and physicalproperties of the material are the same, the pressing pressure and thechange in the electrode-to-electrode distance are proportional to eachother.

As in the above example, the sensor S with the smallestelectrode-to-electrode gap length of all the sensors S is referred to asa sensor S1. The sensor S with the second smallestelectrode-to-electrode gap length is sequentially referred to as asensor S2. Similarly, the sensor S with the nth smallestelectrode-to-electrode gap length is referred to as a sensor Sn. On theother hand, the electrode-to-electrode gap lengths thereof arerespectively denoted by Z1, Z2, Z3 . . . up to Zn. The pressingpressures demanded for respective pairs of the electrodes to come intocontact with each other are denoted by F1, F2, F3 . . . up to Fn. Then,the relationship between the electrode-to-electrode gap length Z1 andpressing pressure F1 can be expressed by the following equation:

Z1=k1×F1  (Equation 1)

where k is a constant determined by the above factors.

Further, the pressure demanded for the electrodes of the sensor S2 tocome into contact with each other after the electrodes of the sensor S1have come into contact with each other is not Z2=k1×F2. The reason forthis is that because the sensor S1 begins to function as a spacer fromthe moment when the electrodes of the sensor S1 come into contact witheach other, the spacer density changes, causing the constant k to becomesmaller.

The relationship between F and Z from when the electrodes of the sensorS1 come into contact with each other to when those of the sensor S2 comeinto contact with each other is as follows:

Z2−Z1=k2×(F2−F1)  (Equation 2)

where k1>k2.

Here, we solve Equation 2 with respect to Z2. Because k1>k2 and fromEquations 1 and 2, Z2 can be expressed as follows:

Z2/F1>(Z2−Z1)/(F2−F1)

Z1×(F2−F1)/F1+Z1>Z2  (Equation 3)

The relationship between k1 and k2 varies depending on the settings ofthe spacer density and sensor S1 density.

Further, the relationship between the n−1th sensor and nth sensor can besimilarly expressed as follows:

Because (k(n−1)>kn),

(Z(n−1)−Z(n−2))/F(n−1)>(Zn−Z(n−1))/(Fn−F(n−1))

(Z(n−1)−Z(n−2))×(Fn−F(n−1))/F(n−1)+Z(n−1)>Zn  (Equation 4)

FIG. 13A illustrates an example of the relationship between the pressingpressure and the change in the electrode-to-electrode gap length whenthe sensors S1 to S6 respectively have the electrode-to-electrode gaplengths Z1 to Z6 as illustrated in FIG. 13B.

Until the electrodes of the sensor S1 come into contact with each other,the pressing pressure and the change in the electrode-to-electrode gaplength show a linear relationship because the spacer density, glassthickness and physical properties of the material remain unchanged.

When the electrodes of the sensor S1 come into contact with each other(when the sensor S1 turns ON), the sensor S1 begins to function as aspacer, thus leading to a higher spacer density. Similarly, each timethe electrodes of the sensor S2, S3 and so on come into contact witheach other, the spacer density will increase, causing the deformationrate to become smaller.

Here, in order for the next sensors to turn ON each time a pressingpressure of 0.2 N is added, the electrode-to-electrode gap lengths Z1 toZ6 of the sensors S1 to S6 need only be set respectively to thedistances Z1 to Z6 shown by dashed lines in FIG. 13A.

This makes it possible to determine the pressing pressure not only assimply being large or small but also quantitatively. For example, if thesensors S1 to S3 are ON, it is possible to determine that a pressingpressure of 0.8 N has been applied.

Of course, the above is merely an example. A variety of types of sensorscan be used as the sensors S1 to Sn.

Further, the electrode-to-electrode gap lengths Z need not necessarilybe set in such a manner as to ensure that the pressing pressures areequidistantly spaced apart (e.g., every 0.2 N).

Still further, if it is only necessary to determine the levels ofgradation of pressing pressure with no need to determine the amount ofpressing pressure itself, the gap lengths Z1 to Zn need not be set tothe distances appropriate to the deformations of the glass substrate.

5. Examples of Arrangement of the Sensors

A description will be given next of examples of arrangement of thesensors S1 to Sn.

FIG. 14A illustrates examples of arrangement of the sensors S1 to S6when these sensors are disposed as shown in FIG. 14H. This figureillustrates an example of stripe type pixel arrangement having thesensors S1 to S6. The sensors having the same electrode-to-electrode gaplengths are arranged with regularity as shown in the figure. In FIGS.14B to 14G, the sensors whose electrodes come into contact with eachother due to the difference in pressing pressure are shown shaded.

FIGS. 15A and 15B and FIGS. 16A and 16B illustrate examples ofcross-sectional structures of the sensors shown respectively in FIGS.14B to 14E with their electrodes into contact with each other.

FIG. 15A illustrates the condition in which only the sensor S1 is turnedON by a small pressure.

FIG. 15B illustrates the condition in which the sensors S1 and S2 areturned ON by a larger pressure.

FIG. 16A illustrates the condition in which the sensors S1, S2 and S3are turned ON by an even larger pressure.

FIG. 16B illustrates the condition in which the sensors S1, S2, S3 andS4 are turned ON by an even larger pressure.

As described above, the sensors turn ON in order from the smallest tolargest electrode-to-electrode gap length as a pressure is applied.Arrangement of the sensors with regularity as illustrated in FIG. 14Aallows for proper determination of the amount of pressing pressure. Thatis, the change in spacer density as a result of the sensors serving asspacers after having turned ON can be quantitatively understood. Thisensures accuracy in the determination of the amount of pressing pressureand facilitates the setting of the electrode-to-electrode gap lengths asdescribed with reference to FIGS. 13A and 13B.

FIG. 17A illustrates another example of arrangement of the sensors. Thisfigure illustrates an example of delta type pixel arrangement having thesensors S1 to S4. Similarly in this case, it is preferred that thesensors having the same electrode-to-electrode gap lengths be arrangedwith regularity.

In FIGS. 17B to 17E, the sensors which turn ON due to the difference inpressing pressure are shown shaded.

6. Effects of the Embodiment and Modification Example

As described above, the present embodiment permits entry of levels ofgradation adapted to distinguish between different pressing pressures byusing the structure which has hitherto been only capable ofdistinguishing between two different states or presence or absence ofcontact.

Such entry of levels of gradation resulting from the intensity of thepressure applied makes it possible to provide, for example, anapplication program which reads the change in writing pressure and drawsbrush-drawn-looking characters and images, despite the fact that theyare pen-drawn. It is also possible to provide an application programwhich permits entry of different values according to the intensity ofthe pressure applied, for example, by a finger.

Further, for example, alarming function can be incorporated in a contacttype touch panel to protect the panel and sensor structure againstexcessive pressing by measuring the amount of pressing pressure. Thisensures use of a contact type touch panel with a proper pressingpressure.

Still further, for example, the orientation of liquid crystal may bedisturbed if the panel is pressed with a large pressure. Only when thepanel is pressed with a large pressure, the pixels pressed with such apressure are identified so that the pixel potentials in a given rangeare adjusted, thus allowing for correction of the disturbed orientation.

It should be noted that a case has been described in the presentembodiment in which the sensor S with the pixel and COM electrodes isprovided in each liquid crystal pixel. However, an embodiment is alsoapplicable to a sensor matrix array which is an array of sensorsarranged in a planar direction and separately from the liquid crystalpixels.

Still further, the display device (display panel) according to anembodiment is not limited to that incorporated in a video recordingdevice, but applicable to a variety of information processing devicesand home electronic appliances such as video reproduction device, audioreproduction device, audio recording device, mobile phone, personalcomputer and PDA (personal digital assistance).

Still further, an embodiment is applicable, for example, to an organicEL (electroluminescence) touch panel.

It should be understood that various changes and modifications to thepresently preferred embodiments described herein will be apparent tothose skilled in the art. Such changes and modifications can be madewithout departing from the spirit and scope of the present subjectmatter and without diminishing its intended advantages. It is thereforeintended that such changes and modifications be covered by the appendedclaims.

The invention is claimed as follows:
 1. A display panel comprising: afirst substrate section formed on the front side of the display panel; asecond substrate section which is opposed to the first substratesection; a liquid crystal; a plurality of pixel sections formed in amatrix form between the first and second substrate sections, each pixelsection including a plurality of pixels; a plurality of sensor sectionsprovided between the first substrate section and the second substratesection, each of the sensor sections having a first electrode and asecond electrode configured so that an electrode-to-electrode gapbetween the first electrode and the second electrode is removed to bringthe first electrode into contact with the second electrode as a resultof a deformation of the first substrate section under pressure, theplurality of sensor sections including a first sensor section and asecond sensor section, the first sensor section having a firstelectrode-to-electrode gap length, the second sensor section having asecond electrode-to-electrode gap length, the firstelectrode-to-electrode gap length being different from the secondelectrode-to-electrode gap length and forming a smallest to largestelectrode-to-electrode gap length; and a circuit for detecting thecontact between the first electrode and the second electrode for each ofthe sensor sections such that the sensor sections turn on from thesmallest to largest electrode-to-electrode gap length as a pressure isapplied, so as to detect an amount of the pressure in multiple levels,wherein the first electrode is provided between the first substratesection and the liquid crystal and the second electrode is providedbetween the second substrate section and the liquid crystal, theplurality of sensor sections form depressed portions of different depthson the first substrate, and the first electrode is arranged on one ofthe depressed portions so as to form a plurality of differentelectrode-to-electrode gap lengths between the first electrode and thesecond electrode.
 2. A display panel comprising: a first substratesection formed on the front side of the display panel; a secondsubstrate section which is opposed to the first substrate section; aliquid crystal; a plurality of pixel sections formed in a matrix formbetween the first and second substrate sections, each pixel sectionincluding a plurality of pixels; a plurality of sensor sections providedbetween the first substrate section and the second substrate section,each of the sensor sections having a first electrode and a secondelectrode configured so that an electrode-to-electrode gap between thefirst electrode and the second electrode is removed to bring the firstelectrode into contact with the second electrode as a result of adeformation of the first substrate section under pressure, the pluralityof sensor sections including a first sensor section and a second sensorsection, the first sensor section having a first electrode-to-electrodegap length, the second sensor section having a secondelectrode-to-electrode gap length, the first electrode-to-electrode gaplength being different from the second electrode-to-electrode gap lengthand forming a smallest to largest electrode-to-electrode gap length; anda circuit for detecting the contact between the first electrode and thesecond electrode for each of the sensor sections such that the sensorsections turn on from the smallest to largest electrode-to-electrode gaplength as a pressure is applied, so as to detect an amount of thepressure in multiple levels, wherein the first electrode is providedbetween the first substrate section and the liquid crystal and thesecond electrode is provided between the second substrate section andthe liquid crystal, the plurality of sensor sections form depressedportions of different depths on the second substrate, and the secondelectrode is arranged on one of the depressed portions so as to form aplurality of different electrode-to-electrode gap lengths between thefirst electrode and the second electrode.
 3. A display devicecomprising: a first substrate section formed on the front side of thedisplay panel; a second substrate section which is opposed to the firstsubstrate section; a plurality of pixel sections formed in a matrix formbetween the first and second substrate sections, each pixel sectionincluding a plurality of pixels; a liquid crystal; a plurality of sensorsections provided between the first substrate section and the secondsubstrate section, each of the sensor sections having a first electrodeand a second electrode configured so that an electrode-to-electrode gapbetween the first electrode and the second electrode is removed to bringthe first electrode into contact with the second electrode as a resultof a deformation of the first substrate section under pressure, theplurality of sensor sections including a first sensor section and asecond sensor section, the first sensor section having a firstelectrode-to-electrode gap length, the second sensor section having asecond electrode-to-electrode gap length, the firstelectrode-to-electrode gap length being different from the secondelectrode-to-electrode gap length and forming a smallest to largestelectrode-to-electrode gap length; a display drive section configured todrive the plurality of pixel sections to display an image; a sensor readsection configured to determine the position of the first substratesection to which a pressure is applied and the amount of pressureapplied thereto by detecting each electrode contact condition at aplurality of sensor sections; and a circuit for detecting the contactbetween the first electrode and the second electrode for each of thesensor sections such that the sensor sections turn on from the smallestto largest electrode-to-electrode gap length as a pressure is applied,so as to detect an amount of the pressure in multiple levels, whereinthe first electrode is provided between the first substrate section andthe liquid crystal and the second electrode is provided between thesecond substrate section and the liquid crystal, the plurality of sensorsections form depressed portions of different depths on the firstsubstrate, and the first electrode is arranged on one of the depressedportions so as to form a plurality of different electrode-to-electrodegap lengths between the first electrode and the second electrode.
 4. Adisplay device comprising: a first substrate section formed on the frontside of the display panel; a second substrate section which is opposedto the first substrate section; a plurality of pixel sections formed ina matrix form between the first and second substrate sections, eachpixel section including a plurality of pixels; a liquid crystal; aplurality of sensor sections provided between the first substratesection and the second substrate section, each of the sensor sectionshaving a first electrode and a second electrode configured so that anelectrode-to-electrode gap between the first electrode and the secondelectrode is removed to bring the first electrode into contact with thesecond electrode as a result of a deformation of the first substratesection under pressure, the plurality of sensor sections including afirst sensor section and a second sensor section, the first sensorsection having a first electrode-to-electrode gap length, the secondsensor section having a second electrode-to-electrode gap length, thefirst electrode-to-electrode gap length being different from the secondelectrode-to-electrode gap length and forming a smallest to largestelectrode-to-electrode gap length; a display drive section configured todrive the plurality of pixel sections to display an image; a sensor readsection configured to determine the position of the first substratesection to which a pressure is applied and the amount of pressureapplied thereto by detecting each electrode contact condition at aplurality of sensor sections; and a circuit for detecting the contactbetween the first electrode and the second electrode for each of thesensor sections such that the sensor sections turn on from the smallestto largest electrode-to-electrode gap length as a pressure is applied,so as to detect an amount of the pressure in multiple levels, whereinthe first electrode is provided between the first substrate section andthe liquid crystal and the second electrode is provided between thesecond substrate section and the liquid crystal, the plurality of sensorsections form depressed portions of different depths on the secondsubstrate, and the second electrode is arranged on one of the depressedportions so as to form a plurality of different electrode-to-electrodegap lengths between the first electrode and the second electrode.